Chemistry assessment September 2016 Flashcards
(39 cards)
Atoms are surrounded by what?
Electrons
What is each atom made up off?
A nucleus which contains protons and neutrons
What is the atomic number?
The number of protons in an atom
How are the elements arranged in the periodic table?
In ascending order of atomic number
The mass number of an atom is what?
Total of protons and neutrons
Atoms of the same element with different numbers of neutrons are called?
Isotopes of that element
Protons and electrons are what?
Oppositely charged
Do neutrons have a charge?
No, they have no charge
Nucleus of an atoms is always…
Positively charged
Why does an atom have a neutral overall charge?
It has the same number of electrons as protons
Protons and neutrons have what?
The same mass
What is the atomic number?
The number of protons in an atom
What is the mass number?
Total number of protons and neutrons in an atom
Where is the mass number shown on a chemical symbol?
At the top
Where is the atomic number shown on a chemical symbol?
At the bottom
What is the isotope of carbon?
-12 or 12C
How do you find out the neutron number on a chemical symbol?
Top number take away the bottom
What did John Dalton do?
He did experiments
Worked out some atomic weights
Invented symbols for atoms and molecules
Some of Dalton’s conclusions…
All matter is made from atoms
Atoms cannot be broken down into anything simpler.
Atoms are rearranged in a chemical reaction.
When was the electron discovered?
1897 by Jj Thompson
What did Jj show us?
That atoms contained smaller pieces
Ernest Rutherford showed us?
Experiments to show that an atom must contain a central nucleus
In an early model, the atom was imagined as what?
A sphere of positive charge with negatively charged electrons.
Radius of a typical atom?
10-10m
Mass- 10-23
